Accurate Excited State Geometries within Reduced Subspace TDDFT/TDA

Area of Science:

• Computational chemistry
• Quantum chemistry
• Theoretical chemistry

Background:

• Calculating excited state geometries is crucial for understanding photophysical processes.
• Traditional time-dependent density functional theory (TDDFT) and Tamm-Dancoff approximation (TDA) methods can be computationally expensive.

Purpose of the Study:

• To develop and test an efficient method for calculating TDDFT/TDA excited state geometries.
• To reduce the computational cost of excited state geometry optimizations.

Main Methods:

• Implementation of a method utilizing a reduced subspace of Kohn-Sham orbitals for TDDFT/TDA calculations.
• Testing the method on fluorophore-like molecules, varying the number of occupied and virtual orbitals included.

Main Results:

• Accurate excited state geometries were obtained for all tested molecules.
• The method achieved efficiency gains of 15-30% compared to standard TDDFT/TDA calculations.
• Similar accuracy was maintained using fewer orbitals than typically required.

Conclusions:

• The reduced subspace method provides an efficient and accurate alternative for TDDFT/TDA excited state geometry optimizations.
• This approach can significantly speed up computational studies of excited-state properties in molecules.